It is prudent never to trust those who have deceived us, even if only once.

It is only prudent never to place complete confidence in that by which we have even once been deceived.

Don't trust the person who has broken faith once.

For trust not him that hath once broken faith

Do not trust all men, but trust men of worth; the former course is silly, the latter a mark of prudence.

Trust no one until you are very sure of the heart to which you open your heart. Learn to mistrust every one; take every precaution for the sake of the love which does not exist as yet.

I only ask you one thing- don't trust nobody

One must never trust the occasion when one is without difficulties.

In those days we did not trust anyone who had not been in the war, but we did not
completely trust anyone.

...we ought not meanwhile to make use of doubt in the conduct of life.

Mind what you do; if you deceive me once I shall never believe you again.

It’s a sign of wisdom to avoid believing every thought that enters your mind. It’s a mark of emotional intelligence to avoid internalizing every feeling that enters your heart.

Don't be reckless with other people's hearts. Don't put up with people who are reckless with yours.

The first was never to accept anything for true which I did not clearly know to be such; that is to say, carefully to avoid precipitancy and prejudice, and to comprise nothing more in my judgment than what was presented to my mind so clearly and distinctly as to exclude all ground of doubt.